1. Field of the Invention
This invention relates to a blasting method capable of effectively removing burrs from a junction part between a large-diameter main bore tubularly drilled through the body of an article, e.g. a component of a fuel feeding system of an internal combustion engine, and a small-diameter branch bore branching off at an angle from the main bore.
2. Description of Related Art
A member having a body 1 in a block form provided with a large-diameter main bore 2 and a small-diameter branch bore 3 branching off at an angle from the main bore 2 as illustrated in FIG. 1, is often used as a component of a fuel feeding system of an internal combustion engine, or the like. When the member is drilled for forming the branch bore 3 to join the main bore 2, the occurrence of burrs in a junction part 8 with the main bore 2 is inevitable, and therefore the removal of the burrs is needed in order for the member to be a finished product. However, the branch bore 3 is often of a small diameter insufficient for the insertion of a tool for deburring. This makes, in the existing conditions, it difficult to remove the burrs from the junction part 8. An electrolytic polishing technique is generally adopted for such deburring. However, this technique involves chemical agents and therefore requires an enormous amount of effort and time for the handling and disposal of the chemical agents with regard to environmental protection. Another attempted method includes a slurry blasting technique of blasting slurry made of a mixture of abrasives and water. In the conventional slurry blasting technique, however, the slurry merely passes linearly through the inside of the main bore 2, and hardly travels toward the small-diameter branch bore 3 which enters the main bore 2. This technique is insufficient to achieve the purpose of removing burrs from the junction part 8.